Introduce branching and support for spark.wap.branch

[cbb330]

Summary

Implement Iceberg table branching functionality in OpenHouse internal catalog with comprehensive testing infrastructure.

The old code was getting unwieldy with nested for-loops, mutable collections, and scattered state management, repeated logic and overall needed a restructure with branching supported first-class. i feel more confident that this is reliable.

Changes

• Branch Operations: Added branch management methods to OpenHouseInternalTableOperations including create, delete, list, and commit reference handling
• Multi-branch Commit Support: Implemented logic to handle commits across different branch references with checks to reject ambiguous commits
• WAP Branch Integration: Added Write-Audit-Publish (WAP) branch support with proper test coverage
• Test Infrastructure: Created comprehensive test suite (BranchTestSpark3_5) covering branch operations, edge cases, and integration scenarios

Changes

• [X] Client-facing API Changes
• [X] Internal API Changes
• [ ] Bug Fixes
• [X] New Features
• [ ] Performance Improvements
• [ ] Code Style
• [X] Refactoring
• [ ] Documentation
• [X] Tests

Testing Done

• [ ] Manually Tested on local docker setup. Please include commands ran, and their output.
• [X] Added new tests for the changes made.
• [X] Updated existing tests to reflect the changes made.
• [ ] No tests added or updated. Please explain why. If unsure, please feel free to ask for help.
• [ ] Some other form of testing like staging or soak time in production. Please explain.

Additional Information

• [ ] Breaking Changes
• [ ] Deprecations
• [ ] Large PR broken into smaller PRs, and PR plan linked in the description.